(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 3
Emissions during the cooling of gaseous chlorine
During condensation of the water in the raw chlorine gas, the condensate gets saturated with
gaseous chlorine. The condensate is usually led through a packed tower, where the chlorine is
stripped from the liquid by means of steam and/or air. To enhance the stripper efficiency,
hydrochloric acid is often added. The chlorine-containing vapour is subsequently fed back into
the raw chlorine collecting main or directed to the chlorine destruction unit. As a rule, emissions
into the atmosphere are avoided.
{The information contained in these paragraphs is contained in chapter 2. There is no
information on emission levels.}
Emissions from the chlorine destruction unit
Most Chlor-alkali plants in EU-27 and EFTA countries have a chlorine destruction unit to
destroy the chlorine present in waste gases. The most common types of chlorine destruction are
the bleach production unit and the hydrochloric acid production unit. Whenever possible, the
residual chlorine is first valorised in bleach or hydrochloric acid production units. Subsequently,
all chlorine production units have a safety chlorine destruction unit for emergency cases and for
removal of the unused residual gas. The absorption of chlorine in caustic soda is most
commonly used for chlorine destruction [ 3, Euro Chlor 2011 ]. Reported emission levels at the
outlet of this unit are highly variable and are often below the detection limit (see Table 3.18).
The specific emissions lie in the range of 0.5 – 2 g Cl2 per tonne of chlorine production
capacity. [Dutch report, 1998].
Table 3.18: Emissions of chlorine to air from chlor-alkali plants in EU-27 and EFTA countries
in 2008/2009
Chlorine emission concentrations in mg/m 3 ( 1 ) ( 2 )
Value
reported ( 3 10th 25th
Min.
)
percentile percentile Median
75th 90th
Max.
percentile percentile
Min. ( 4 ) 0.0029 0.025 0.065 0.24 0.68 1.1 2.0
Max. ( 5 ) 0.05 0.31 1.0 2.0 3.2 7.3 47
Average ( 6 ) 0.20 ND 0.88 2.4 7.0 ND 20
Chlorine emission factors in g per tonne of annual chlorine capacity ( 1 ) ( 2 )
Value
reported ( 3 10th 25th
Min.
)
percentile percentile Median
75th 90th
Max.
percentile percentile
Min. ( 7 ) 0.000050 0.020 0.028 0.17 0.23 2.5 2.7
Max. ( 8 ) 0.040 0.069 0.11 0.54 2.2 6.6 13
Average ( 9 ) 0.0080 ND 0.010 0.035 0.30 ND 2.4
( 1 ) Data refer to the outlet of the chlorine absorption/destruction unit under standard conditions (273.15 K, 101.3
kPa).
( 2 ) About half of the reporting plants perform continuous measurements while the other half performs periodic
measurements (mostly semi-monthly, quarterly and semi-yearly). Averaging periods reported were mostly halfhourly
and hourly.
( 3 ) Some plants reported ranges with minimum and maximum values, some reported average values and some
reported both.
( 4 ) 14 data from 14 plants. In addition, 16 plants reported values below the detection limit, 1 plant a value of
< 0.19 mg/m 3 , 1 plant a value of < 1 mg/m 3 and 2 plants a value of < 10 mg/m 3 .
( 5 ) 29 data from 29 plants. In addition, 1 plant reported a value below detection the limit, 1 plant a value of
< 0.19 mg/m 3 , 1 plant a value of < 1 mg/m 3 and 2 plants a value of < 10 mg/m 3 .
( 6 ) 8 data from 8 plants.
( 7 ) 12 data from 12 plants. In addition, 7 plants reported values below the detection limit and 1 plant a value
of < 1.4 g/t.
( 8 ) 8 data from 8 plants. In addition, 1 plant reported a value of < 1.4 g/t.
( 9 ) 20 data from 20 plants. In addition, 2 plants reported a value of < 15 g/t.
NB: ND = not enough data.
Source: [ 57, EIPPCB 2011 ]
WORKING DRAFT IN PROGRESS
96 December 2011 TB/EIPPCB/CAK_Draft_1